In the field of the medical diagnosis, conventionally, an X-ray CT (Computerized Tomography) imaging apparatus is a photographing apparatus in which an X-ray beam of a predetermined amount is transmitted to a patient's site to be imaged or photographed, the transmitted X-ray amount is measured by an X-ray sensor and the measured data is recorded in a memory, and an X-ray absorbing rate of each point of the captured bodily region of the patient is obtained by a computer and is reconstructed into an image. In the field of the dental diagnosis, an X-ray panoramic photographing apparatus is an apparatus for conducting tomography while rotating along a locus suitable for the form of a dental arch.
The conventional X-ray CT photographing apparatus can obtain only a CT image, and the conventional panoramic photographing apparatus can obtain only a photographic image. Therefore, recently, combined panoramic and computed tomography photographing apparatuses have been proposed.
U.S. Pat. No. 6,118,842 discloses an X-ray imaging apparatus which can conduct both the CT imaging and the panoramic imaging. The apparatus includes: an X-ray source for generating X-rays, an X-ray sensor for detecting X-rays having passed through an object, and supporting means for supporting the X-ray source and the X-ray sensor so that the X-ray source and the X-ray sensor are opposed to each other across an object; and mode switching means for switching between a CT mode and a panorama mode. To detect X-rays, only one X-ray sensor is used, and the X-ray sensor is an area sensor which is capable to detect a large area. The X-ray imaging apparatus can obtain the tomography image by converting the photographic mode into the panoramic mode after obtaining the CT image by selecting the CT mode.
However, the conventional imaging apparatus conducts the CT photographing and the panoramic photographing using only one sensor, and hence, needs an expensive sensor capable of carrying out the two photographing functions. Additionally, the conventional imaging apparatus has another problem in that it is difficult to obtain the optimum image according to the CT photographing or the panoramic photographing since a distance between the X-ray sensor and the X-ray source is uniform.